A nonwoven is widely used as a replacement for traditional textile products in numerous sectors, for example in the field of surface cleaning and protection, or in the production of garments. Compared to conventional fabrics, the nonwovens have the advantage of lower production costs, outstanding mechanical properties and a high biocompatibility with skin.
Among the nonwovens, those of the spunbonded type are formed either by synthetic (polymer) or natural material fibres which are laid on a mat in the form of a layer after being solidified when just coming out from the spinneret and subsequently attenuated at a prefixed distance from the spinneret by the application of forced air substantially at ambient temperature. The material forming said fibres is conventionally subjected to a stretching or elongation force causing the formation of continuous filaments.
The thus obtained structure can be consolidated by dynamic treatments such as bonding by stitches or by weft (calendering), or by jets of water (hydro-entanglement). Other bonding methods known in the field are mechanical needling, thermobonding, chemical bonding.
Generally, the spunbonding methods provide the extrusion of thermoplastic polymers through spinnerets such as to form a plurality of continuous filaments. These filaments, which are first solidified and then elongated, typically by means of a high-speed fluid, are random laid on a collecting surface such as a conveyor belt and form a non-consolidated ply. Subsequently, the filaments are bonded to provide the final ply having cohesion and strength characteristics.
The bonding step can be obtained by directly applying heat and pressure to the non-consolidated ply by means of heated calenders.
Particularly, after the non-consolidated ply has been laid down, it is carried on said conveyor belt to the calenders where it leaves the belt and is taken by two calender rolls to be heated and crushed. Thereby, the polymer ply is only carried until reaching the calenders and both rollers of the same calenders also act as the supports/conveyors as well as consolidators for the ply.
The product resulting from said method is normally in the form of a very thin ply, in the range of 0.18-0.3 mm weighing 15-17 g/m2, compact, of threadlike appearance, and provided by slightly embossed patterns defined by the gaps between the cohesion points of the calender design.
Such a product, though showing good cohesion properties, is not very suitable for use in the hygiene sector, and however in those sectors requiring particular performance in terms of softness and thickness.
In addition, the cohesion is not sufficient when the product is used for instance in the cleaning field or as garments so that the product easily tends to wear out and, further, tends to cause a undesirable “pilling” effect particularly when the cohesion is carried out by hydroentangled technology, i.e. formation of fine loops onto the surface of the final product which engage with the roughness of for instance hands during using.